1. Field of the Invention
This invention relates to a lens barrel retracting device which is capable of stowing a lens barrel into a camera body in a very compact state and more particularly to a lens barrel retracting device suited for a compact zoom camera.
2. Description of the Related Art
In positioning the front and rear lens groups of a photo-taking optical system for continuously changing the focal length of the system, the conventional compact zoom camera has been arranged to perform zooming by restricting their positions with a cam ring 201 and a straight movement cam 202 as shown in FIG. 18 of the accompanying drawings. In retracting the lens barrel 203 of an optical system, which is shown in a wide-angle position in FIG. 18, the cam ring 201 is caused to further rotate from its wide-angle position until the tip of the lens barrel 203 comes to be flush with the fore end part of a cover 204.
However, the conventional lens barrel retracting arrangement has presented the following problems:
(i) The arrangement of the cam ring provided for restricting the positions of the front and rear lens groups of the photo-taking optical system necessitates the barrel retraction to be carried out with the photo-taking optical system in the wide-angle position, in which some interval space is left between the front and, rear lens groups. This space causes an increase in the thickness of the camera in the state of having the lens barrel retracted.
(ii) The space left between the front and rear lens groups at the time of lens barrel retraction may be shortened by providing, as shown in FIG. 19, a cutout part 201a in a part extending the wide-angle end 201b of the cam slot of the cam ring 201 which is arranged to restrict the position of the rear lens group. However, although the space between the front and rear lens groups can be shortened by the provision of the cutout part 201a, this brings about no substantial change in length of the cam ring 201 in the direction of an optical axis, as shown in FIG. 20. Therefore, the desired reduction in the thickness of the camera in the lens-barrel-retracted state is still hindered by the length of the cam ring 201. Nevertheless, the thickness of the camera is not much changed from the thickness mentioned in Para. (i) above.
(iii) FIG. 21 shows an attempt to increase the lens barrel retracting degree. In this case, another cam ring 205 and another straight movement cam 206 are arranged on the periphery of the straight movement cam 202 to engage a pin 207 provided on the straight movement cam 202. This arrangement enables the whole lens barrel to be retracted by rotating the cam ring 205. However, this arrangement necessitates the addition of the cam ring 205 and the straight movement cam 206, which increases the size of the lens barrel part of the camera. As a result, the camera becomes larger as a whole.
(iv) Further, according to the above-stated method, a zooming power transmission gear 208 must be arranged in a position not to interfere with the movement of the cam ring 205 and the straight movement cam 206, as shown in FIG. 21. To meet this requirement, the external cover 209 of the camera must be set in a further forward position. Therefore, the method of using the lens barrel retracting cam ring 205 and the straight movement cam 206 not only fails to sufficiently reduce the thickness of the camera but also merely results in a more complex mechanism.
(v) Further, in order that a peripheral gear part 201c of the cam ring 201 which is arranged as shown in FIG. 22 to engage the above-stated gear 208 for zooming is positioned not to interfere with the inner circumferential part of the above-stated straight movement cam 206, the cam 206 and the cam ring 205 must be arranged to have large diameters. However, that arrangement increases the size of the camera.
(vi) In order that the above-stated gear 208 is kept in a state of engaging the gear part 201c when the lens barrel is retracted, it is necessary to extend the gear part 201c of the cam ring 201 as indicated by a part 201d in FIG. 22. However, the extended gear part 201d must be covered with the external cover 209 of the camera in such a way as to prevent it from being exposed to the outside even when the gear part 201d is drawn out and forward from the lens barrel retracted position. This requires a larger outside diameter of the lens barrel cover.
(vii) If the cam ring 201 is exposed to the outside when the lens barrel is drawn out from its retracted position, the cam slot of the cam ring 201 would also be exposed. This is not only detrimental to the appearance of the camera but also might incur a leak of light from the cam slot. To prevent this, the external cover 209 must be provided with an extension part 209a covering the cam ring 201 and the straight movement cam 202 even when the lens barrel is drawn out from its retracted position, as shown in FIG. 22. To meet that requirement, the camera must be designed to have a larger thickness than the conventional product although the lens barrel can be completely retracted.